Grass-Cutting Head with Spiral Guide Channels for the Cutting Line

ABSTRACT

The grass-cutting head ( 101 ) has a body ( 103 ) forming a housing for at least one spool of cutting line (F 1 ; F 2 ), provided with at least one outlet hole ( 111 ) of an end of the cutting line wound on said spool positioned inside the head. For each outlet hole, a guide channel for the cutting line is also provided, extending from the inside of the housing towards the hole and having an inclined trend, gradually moving away from said axis of rotation.

TECHNICAL FIELD

The present invention relates to a grass-cutting head for cuttingvegetation, and more specifically to a grass-cutting head of the linetype, that is, in which the cutting member is composed of a lineprojecting radially from the head, and which cuts the surroundingvegetation through centrifugal force.

STATE OF THE ART

For gardening jobs, both at amateur and professional level,grass-cutting heads are commonly used to cut grass and other vegetation,provided with cutting lines projecting radially from a main body of thehead and which, thanks to the centrifugal force exerted thereon and tothe rapid rotation of the head about the axis thereof, cut thevegetation.

Examples of cutting heads of this type are described in the followingUnited States patents: U.S. Pat. No. 4,097,991, U.S. Pat. No. 4,104,797,U.S. Pat. No. 4,145,809, U.S. Pat. No. 4,161,820, U.S. Pat. No.4,259,782, U.S. Pat. No. 4,203,212, U.S. Pat. No. 4,274,201, U.S. Pat.No. 4,651,421, U.S. Pat. No. 4,738,085, U.S. Pat. No. 4,805,306, U.S.Pat. No. 4,813,140, U.S. Pat. No. 4,823,465, U.S. Pat. No. 4,882,843,U.S. Pat. No. 4,893,410, U.S. Pat. No. 4,942,664, U.S. Pat. No.4,959,904, U.S. Pat. No. 4,989,321, U.S. Pat. No. 5,010,649, U.S. Pat.No. 5,526,572, U.S. Pat. No. 5,095,688, U.S. Pat. No. 5,136,782, U.S.Pat. No. 5,295,306, U.S. Pat. No. 5,490,641, U.S. Pat. No. 5,657,542,U.S. Pat. No. 6,141,879, U.S. Pat. No. 6,163,964, U.S. Pat. No.6,851,191.

In conventional grass-cutting heads, the outlet hole of the cutting linecan be produced directly in the body forming the housing of the linespool (as in U.S. Pat. No. 4,148,141), or in metal bushings inserted inrespective seats produced in the perimeter wall, typically cylindrical,of the body housing the spool (U.S. Pat. No. 4,097,991).

U.S. Pat. No. 4,271,595 describes a grass-cutting head of the line typewherein two cutting lines project from the body of the head inclinedwith respect to the radial direction. For this purpose the bushingsdefining the outlet holes of the lines have a channel for the lines topass through with a rectilinear but substantially inclined trend withrespect to the radial direction, instead of being parallel to saiddirection as in the case of conventional grass-cutting devices. Thisparticular arrangement has the function of reducing wear and overheatingof the line at high head rotation speeds. The hole of the bushing opensonto the cylindrical surface of the body of the head.

In all conventional heads, including the head produced as indicated inU.S. Pat. No. 4,271,595, the cutting line is subject to frequentbreakages due to high impact against any obstructions which may bepresent around the grass-cutting head (such as stones, clods of hardsoil or the like) and also due to any particularly coarse vegetationpresent. Breakage of the line often occurs at the level of the holethrough which the line is fed from the body forming the housing for thespool on which the cutting line is wound. When this occurs, considerabledifficulties can be encountered when passing a new portion of linerequired to continue with the cutting operation through the hole. Inparticular, if the spool accidentally rotates even by a slight angleafter breakage of the line, the severed end of the cutting line retractscompletely inside the body of the head and said body must be opened topass the end of the line into the bushing or hole to make it projectfrom the body of the head through said hole by a length sufficient toallow correct operation of the lengthening devices with whichgrass-cutting heads are normally provided.

U.S. Pat. No. 4,114,269 describes a grass-cutting head of the line type,wherein the outlet hole of the cutting line is delimited by tworectilinear edges, parallel to the axis of rotation of the head. Thefront edge, or the edge farther forward with respect to the direction ofrotation of the head, has a tear-drop shaped cross section, that is,which is thicker than the remaining part of the approximatelycylindrical wall of the body housing the cutting spool, in which wallthe outlet holes of the cutting line are produced. This conformation hasthe object of reducing strains and overheating of the line, but does notovercome the aforesaid drawbacks, related to retraction of the brokenend of the line into the housing of the spool.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to produce a grass-cutting headwhich overcomes entirely or in part the aforesaid drawbacks and which inparticular reduces the tendency of the line to break due to impact withobstructions surrounding the head during cutting and/or facilitatesprojection of the line, even if it breaks at the level of the outlethole, or at the level of the outlet bushing from the body of the head.

These and other objects and advantages, which shall be apparent to thoseskilled in the art from reading the text hereunder, are obtained insubstance with a head as claimed in claim 1, The dependent claims relateto further possible and advantageous features of the invention.

In, substance, the invention provides a grass-cutting head with an axisof rotation and a body forming the housing for at least one spool ofcutting line, provided with at least one outlet hole of an end of saidcutting line wound on said spool, which also comprises, for each hole, aguide channel for the cutting line, extending from the inside of saidhousing towards the outlet hole and having an inclined development,gradually moving away from said axis of rotation. According to anadvantageous embodiment, the outlet hole is on a surface inclined by anangle differing from 90° with respect to a radial plane containing theaxis of rotation and passing through the center of the hole. Insubstance, in the preferred embodiment, the hole or each hole is locatedon a surface which intersects a substantially cylindrical wall of thebody of the head.

In practice, the channel is produced in portions of the body of the headwhich project gradually with respect to a basic shape substantially witha circular section of said body and the line is fed from saidprojections with a non-radial orientation, but inclined with respect toa radial plane. In this way improved operation of the head is obtained,with regard to the consequences of impact with possible obstructionsaround the head during operation.

In a practical embodiment, the outlet hole or each outlet hole candefine a direction of projection of the line from the body of the headinclined by an angle between 30° and 90° and preferably between 60° and90° with respect to a radial direction.

The guide channel of the cutting line can have, preferably, anapproximately spiral shape, where spiral is intended generally as acurve which has a variable radius of curvature to move gradually awayfrom an axis or center, coincident with the axis of rotation of thegrass-cutting head.

Preferably, the surface on which the outlet hole is located forms withsaid radial plane an angle between 0° and 80°, preferably between 0° and45° and even more preferably between 0° and 30°.

According to a possible embodiment of the head according to theinvention, associated with each of the outlet holes of the line arerespective tangential tabs, projecting with respect to the body of thegrass-cutting head. These tabs (advantageously arranged on theprojections inside which the guide channels of the lines are produced)can be interchangeable and optionally provided with toothing, i.e.serrated on the surface radially facing towards the outside of the head.

In a possible embodiment, in a top plan view the body of the head has asubstantially circular shape and, for said hole or for each of saidholes, integral with said body is a projection with a radiallyincreasing extension, inside which said guide channel extends. Theprofile of the projections is preferably approximately a portion ofspiral.

In a possible embodiment, the body of the grass-cutting head comprises:a cup portion, defining a housing for the spool of cutting line; anannular portion coupled to said cup portion, defining, together withsaid cup portion, said guide channel or channels; and a removableclosing member.

According to an advantageous embodiment, each of said guide channelsextends along an angle equal to at least 30°, preferably equal to orgreater than 45° and even more preferably equal to or greater than 60°,for example also between 80° and 120°, about the axis of rotation ofsaid grass-cutting head.

According to a different aspect, the present invention relates to agrass-cutting head with an axis of rotation and a body forming a housingfor at least one spool of cutting line, provided with at least oneoutlet hole of an end of said cutting line wound on the spool, which hasa toothed outer profile, a respective outlet hole of the cutting linebeing positioned at the level of each tooth of said profile. Thegrass-cutting head as a whole will therefore no longer have, in a topplan view, the conventional circular shape, but will be characterized bythe projections forming said teeth, at the level of which the lineprojects with a non-radial direction of projection.

In practice, each tooth of said toothed profile has a first sideinclined by an angle not exceeding 45° and preferably between 0° and 30°with respect to a radial direction, on which the respective outlet holeof the line is produced. Moreover, according to a preferred embodimentof the invention each tooth has a second curvilinear side with apreferably approximately spiral development. A guide channel for thecutting line extends inside each of said teeth.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be better understood by following the descriptionand accompanying drawing, which shows practical non-limiting examples ofembodiment of the invention. More specifically, in the drawing:

FIGS. 1 and 2 show a bottom view and a top view of a grass-cutting headaccording to the invention in a first embodiment, from which an optionalcover has been removed to view the internal structure;

FIGS. 3 and 4 show perspective views according to two different anglesof the head in FIGS. 1 and 2;

FIG. 5 shows a perspective view of a head analogous to the head in FIGS.1 to 4, but configured for a greater number of cutting lines;

FIG. 6 shows a plan view according to VI-VI in FIG. 5;

FIG. 7 shows an exploded axonometric view of a head according to animproved embodiment of the invention;

FIG. 8 shows a perspective view of the head in FIG. 7 in an assembledlayout;

FIG. 9 shows a sectional perspective view according to a diametric planeof the head in FIGS. 7 and 8;

FIG. 10 shows a side view of the head in FIGS. 7 to 9;

FIGS. 11 to 14 show views and sections according to transverse planeswith trace XI-XI; XII-XII; XIII-XIII and XIV-XIV of FIG. 10respectively, wherein in FIG. 13 the head is shown without the closingcover;

FIG. 15 shows a perspective view of a modified embodiment of the head;and

FIGS. 16 and 17 show a perspective view and a section according to amedian plane of a head in a further embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

With initial reference to FIG. 1 to 4, in a first embodiment thegrass-cutting head according to the invention, indicated as a whole with1, has a body 3 composed of a main part substantially in the form of acasing, shown in FIGS. 1 to 4, and optionally a closing cover, notshown, which defines with the cup portion, a compartment 13 to house aspool, indicated schematically with 5 (FIGS. 2 and 4), on which one ormore cutting lines F1, F2, are wound. Externally, the body 3 of thegrass-cutting head 1 has a substantially circular extension in a topplan view, the maximum diameter of which is defined by the diameter of acircular flange 7. Extending under the circular flange 7, with basicconformation with a substantially circular section of the body 3, aretwo projections indicated with 9.

These projections have an approximately spiral development, in the sensethat they are defined by an external curvilinear surface 9A which movesgradually away from the body of the head 3, from a point 9B ofconnection with the cylindrical wall of the body 3, to a point 9C ofmaximum radial distance from the axis of rotation A-A of thegrass-cutting head. Moreover, each projection 9 has a flat surface (inthe example shown) indicated with 9D, which has an inclination of anangle β (FIG. 2) with respect to a radial plane, that is, a planecontaining the axis of rotation A-A, passing through the central area ofthe surface 9D. The angle formed by the direction of projection of thecutting line F1, F2 with respect to the radial direction, is indicatedwith γ. The sum of the angles β and γ can be equal to 90° if the lineprojects orthogonally to the frontal surface 9D of the projection 9, butthis is not binding, as can be seen in the example shown.

In practice, the projections 9 form teeth projecting from the body ofthe grass-cutting head 1, which in the example shown have sides (9A, 9D)differing from each other in shape and/or inclination.

In an approximately central position the surface 9D has a hole 11 from,which the cutting line F1 or F2 project. In the example shown the hole11 is produced directly in the base material forming the body 3 (or thelower part of said body) and the projections 9. It would also bepossible for the hole 11 to be formed in a bushing inserted inside thebase material forming the projection 9 and/or the body 3.

As can be seen in particular in FIGS. 2 and 4, both a housing, indicatedwith 13, for the spool 5, and a pair of guide channels 15 produced inthe material forming the projections 9 extending more or less spirally,are defined inside the body 3. Each of these channels has an inlet,which is radially innermost at the level of a rounded corner 15Aproduced in the base material forming the body 3, and an outlet at thelevel of the respective outlet hole 11 of the cutting line F1 or F2,said hole defining the radially outermost point of the channel.Alternatively, the channels can be made of a different material to thebase material of the head of the body, for example by metal insertsinserted in an injection mold for plastic materials. The projections 9can also be made of the same material as the body 3 or of a differentmaterial, optionally molded together with the body 3 or by insertsarranged in the mold prior to injection of the resin with which the body3 can be made. Alternatively, the head can be made of metal parts.

Each guide channel 15 therefore extends for an angle α (FIG. 2) aboutthe axis of rotation A-A of the grass-cutting head. The line F1, F2projects with the free end thereof from the respective hole 11 in adirection which substantially forms the extension of the spiral definingthe median line of the channel 15. It must be understood that spiralshape is intended herein not necessarily as a spiral in a mathematicalor geometric sense, but in the more general sense a shape of the channel15, wherein this extends from the inlet (at the level of the edge 15A)to the outlet formed by the hole 11 extending gradually away from theaxis A-A in a radial direction outwards. If necessary, the channel 15could have a conformation which is rectilinear or formed of rectilinearportions with gradually variable angles from the inlet to the outlet.

With this configuration two positive effects are substantially obtained.On the one hand, when the head rotates (the direction of rotation isindicated with the arrow F in FIG. 1) the side surface, that is the side9A of each of the two projections 9, tends to move any obstructions,such as stones, clods of hardened soil, particularly coarse vegetationor the like, away from the hole 11 so that these obstructions do notknock against the line F1 or F2 too close to the point at which itprojects from the grass-cutting head 1. This means that any breakage ofthe line caused by a violent impact against an obstruction occurs at acertain distance from the outlet hole 11, thereby avoiding the risk ofthe free end of the severed line remaining inside the body 3 of the head1.

In the second place, even if breakage of the line were to take place atthe level of the hole 11, subsequent projection of a new portion of lineF1, F2, to restore the cutting function of the grass-cutting head 1,would nonetheless be possible thanks to the fact that a large portion ofthe last turn of cutting line F1, F2 inside the grass-cutting head 1 isguided in the respective spiral channel 15. Contrary to the case ofconventional heads, therefore, even if the line were to break close tothe wall of the head and, therefore, to the hole 11, this would not makeit impossible to restore the cutting length of the said line.

The angular extension a of the guide channel 15 does not necessarilyhave to be as wide as shown in FIGS. 1 to 4 (here approximately equal toor slightly greater than 90°). On the contrary, this angle can also beequal to 60° or less, although a relatively wide angle is particularlyuseful to guarantee the second function described above.

FIGS. 5 and 6 show, in a perspective view and in a bottom plan viewaccording to VI-VI in FIG. 5, a slightly modified embodiment of the headdescribed above. The same numbers indicate the same or equivalent partsto those of the previous embodiment. In this case, the body 3 of thehead, or more precisely the lower part of said body, has fourprojections 9 rather than two, so that four cutting lines (not shown)can project from the respective holes 11 on the grass-cutting head 1. Inthis case the angle α along which the four guide channels 15 extend willbe slightly below 90°.

FIG. 7 to 14 show an improved embodiment of the head according to theinvention. The head, indicated as a whole with 101, has a body 103formed by a cup portion 103A, an annular portion 103B coupledpermanently to the portion 103A (i.e. even by gluing, welding or thelike, or with screws, rivets, pins or in another way) and a cover 103Cremovable to allow access to the inside of a compartment housing thespool of cutting line. This compartment is defined by the portions 103Aand 103B of the body 103. In this embodiment, the spool, indicated with105, is produced as shown in U.S. Pat. No. 6,851,191, the content ofwhich is explicitly referred to here as an integral part of the presentdescription, and which can be referred to for further constructionaldetails.

Inside, this spool 105 is an elastically stressed slider 106,cooperating with a double series of toothings produced on the inside ofthe hub of the spool 105, to allow lengthening of the line wound on saidspool. The slider 106 slides axially on a pin 108 torsionally coupled tothe portion 103A of the body 103 of the head. There is a torsionalcoupling also between the slider 106 and the pin 108 composed of aseries of grooves 108A (FIG. 7) on the pin 108 and corresponding teethon the slider 106. The movement according to the double arrow f106 ofthe slider 106 is obtained by a button 110 projecting through a hole103D produced in the central part of the cover 103C. The button 110projects downwards from the head, when this is mounted on the brushcutter or other operating device, so that the user can press therotating head on the ground and thereby cause repeated actions ofalternate sliding on the slider 106 and consequent lengthening in stepsof the cuffing line wound on the spool 105, all as described in greaterdetail in the aforesaid U.S. Pat. No. 6,851,191.

The cover 103C has elastic tabs 103E with which it connects in notches103F produced in the annular portion 103B of the body 103 of the head.The elastic tabs 103E are accessible from the outside (FIG. 8) so that,by means of pressure thereon, the cover 103C can be released from thebody 103 formed by the portions 103A, 103B of the head 101.

Once the portions 103A and 103B of the body 103 of the grass-cuttinghead 101 are coupled together they define a body having a basicextension with a substantially circular section, from which projections109, produced in part on the portion 103A and in part on the portion103B of the body 103, project in a radial direction. The projections 109have an approximately spiral conformation, in the sense that theirsurface or side wall 109A has an approximately spiral trend (in the planview), moving gradually away from the axis A-A of rotation of the headstarting from a point 109B of connection to a substantially cylindricalsurface of the central body 103 until reaching an area 109C of maximumradial dimension. Each projection 109 also has an approximately radialsurface 109D onto which a respective outlet hole 111 of the cutting lineopens. The direction of exit of the cutting line is therefore in thiscase substantially tangential, that is, substantially orthogonal to aplane passing through the axis of rotation A-A of the head.

The projections 109 are produced as mentioned above in part in thematerial forming the portion 103A and in part in the material formingthe portion 103B of the body 103 (see FIG. 7). Coupling of these twoportions forms a channel 115 through which the respective cutting line(not shown) is guided. In substance, each of the two channels 115extends from a rounded corner 115A with a substantially spiral extensionto the front surface 109D of the respective projection 109.

In the example shown respective tangential tabs, which in this specificembodiment are interchangeable, are associated and made integral witheach of the two projections 109. For this purpose, each tab 121 has asystem for connection to i.e. reversible engagement with the body 103 ofthe grass-cutting head 101. To obtain this reversible engagement, in theembodiment shown, each tab 121 has a first hook-shaped end 121A which isinserted into a corresponding recess 131 produced in the projection 109.The opposite end 121B of each tab 121 has a through hole 121C (i.e.shaped like an eyelet) and is positioned at the level of the outlet hole111 of the cutting line. As can be seen in particular in FIG. 9, in thisembodiment the interchangeable tab 121 actually forms one side of thehole 111. Due to how the tab 121 is positioned, the end 121B thereofdefines a supporting surface for the cutting line.

Each tangential tab 121 is connected to the respective projection 109 byfirst inserting the hook shaped end 121A into the corresponding recess131 and then inserting the entire interchangeable tab into the seatdefined between the two coupled portions 103A, 103B. A pin, a screw orthe like is inserted into a hole 133 of the projection 109, which is inalignment with the through hole 121C of the respective tab 121. Thetangential tab 121 is thus permanently fastened to the head untilsubsequent removal of the screw, pin or the like inserted in the hole133, to allow replacement of the tab 121, for example due to wear.

As can be seen in particular in FIGS. 7 and 8, once the portions 103A,103B and the tabs 121 have been assembled, the guide channel 115 isactually delimited in part by walls formed of the material of which thebody 103 (more specifically the portions 103A, 103B thereof) of thegrass-cutting head 101 is composed and in part by the radially inwardfacing surface 121E (FIG. 7) of the respective tangential tab 121.

It would also be possible to omit the tabs 121 and to produce the body103 of the head 101 solely with two portions 103A, 103B coupled to eachother, besides the cover 103C. The outlet hole 111 of the line couldalso be defined in a bushing, possibly made of metal, inserted in thematerial forming the respective projection 109. However, the use ofinterchangeable tangential tabs 121 is particularly advantageous becauseit allows worn tabs to be replaced with new ones, preserving theintegrity of the body 103 of the head. Tabs made of a sturdier materialthan the material forming the body 103 of the grass-cutting head 101allow the useful life of the head to be prolonged even if they are notinterchangeable, thanks to their increased durability. For example, thetabs could be made of metal and the rest of the head of molded syntheticresin. The increase in cost which this implies compared to a headentirely made of synthetic resin is slight, as the tabs have a limitedmass. Alternatively, the tabs could be made of the same material as thebody 103. In this case, they form a sort of deposit of material which,although becoming worn, protects the remaining part of the head frompremature wear.

Moreover, it is also possible to use interchangeable tangential tabs 121of a different shape depending on the type of vegetation to be cut. Forexample, when cutting particularly coarse grass, it is possible to usetangential tabs 121 which have a toothing on the surface facing radiallyoutward, said toothing performing severing of coarser vegetation.

In any case, the tangential tabs 121 offer further protection againstbreakage of the cutting line caused by impact thereof againstobstructions present which may be found around the grass-cutting headduring use.

FIG. 15 shows a perspective view of the head in FIGS. 7 to 14, modifiedas regards the form of the tabs, here indicated with 121X. The samenumbers indicate the same or equivalent parts to those in FIGS. 7 to 14.The tabs 121X are produced, in this case, with an outer toothing 121D.This toothing has the function of severing or weakening the vegetationor other obstructions, such as clods of earth, which may be found aroundthe head during use thereof, so as to perform a mechanical actionpreliminary to the cutting action of the line F1, F2.

FIGS. 16 and 17 show a different configuration of the head, wherein theoutlet holes of the cutting line are radial rather than inclined towardsthe tangential direction. As can be seen in FIG. 17, which represents asection along a plane separating the portions 3A and 3B of the body 3 ofthe head, housed therein is a spool 5 wound on which is the cutting linewhich projects through radial holes produced in bushings 201 inserted inthe body of the head 1. Between the spool 5 and each outlet hole of eachbushing 201 a respective channel 15 is produced, substantially spiral inshape and defined by two surfaces 15B, 15C, the inlet of which isdefined by a rounded corner 15A. The shape of the channels 15 issubstantially equivalent to that of the channels shown in FIGS. 1 and 2,with the difference that they end at the level of the bushings withradial outlet 201.

It is understood that the drawing only shows an embodiment provided byway of a practical example of the finding, which may vary in forms andarrangements without however departing from the scope of the concept onwhich said finding is based.

1. A grass-cutting head with an axis of rotation, the grass-cutting headcomprising: a body forming a housing for at least one spool of cuttingline, provided with at least one outlet hole of an end of said cuttingline wound on said spool; a guide channel in communication with said atleast one outlet hole for receiving the cutting line, said guide channelextending from the inside of said housing towards the outlet hole andhaving an inclined shape, gradually moving away from said axis ofrotation.
 2. Grass-cutting head as claimed in claim 1, wherein saidoutlet hole is on a surface inclined by an angle differing from 90° withrespect to a radial plane containing the axis of rotation and passingthrough the center of the hole.
 3. Grass-cutting head as claimed inclaim 1, wherein said channel and said outlet hole are produced inportions of the body of the head projecting with respect to asubstantially cylindrical surface of said body, the hole being locatedon a surface which intersects said substantially cylindrical surface. 4.Grass-cutting head as claimed in claim 1, wherein the outlet holedefines a direction of projection of the line from the body of the headwhich is not radial and preferably inclined by an angle between 30° and90° and more preferably between 60° and 90° with respect to a radialdirection and even more preferably between 60° and 90°.
 5. Grass-cuttinghead as claimed in claim 1, wherein said guide channel has anapproximately spiral shape.
 6. Grass-cutting head as claimed in claim 5,wherein the surface on which the outlet hole is located forms with aradial plane an angle between 0° and 80°, preferably between 0° and 45°and even more preferably between 0° and 30°.
 7. Grass-cutting head asclaimed in claim 5, wherein the surface on which the outlet hole islocated has a substantially radial extension with respect to the axis ofrotation of the head.
 8. Grass-cutting head as claimed in claim 1,wherein associated with said outlet hole are respective tangential tabs,projecting with respect to said body.
 9. Grass-cutting head as claimedin claim 8, wherein said tangential tabs are interchangeable. 10.Grass-cutting head as claimed in claim 8, wherein said tabs have toothedprojections.
 11. Grass-cutting head as claimed in claim 1, wherein in atop plan view said body has a substantially circular extension and, forsaid hole, integral with said body is a projection with a radiallyincreasing extension, inside which said guide channel extends. 12.Grass-cutting head as claimed in claim 11, wherein the profile of saidprojection is preferably approximately a portion of spiral. 13.Grass-cutting head as claimed in claim 11, wherein said projection ismade integral with said body, with the same material of which said bodyis formed or with a different material.
 14. Grass-cutting head asclaimed in claim 11, wherein integral with said projection arerespective tangential tabs, extending radially beyond the profile of therespective projection.
 15. Grass-cutting head as claimed in claim 14,wherein said tangential tabs are interchangeable.
 16. Grass-cutting headas claimed in claim 14, wherein said tangential tabs have toothedprojections.
 17. Grass-cutting head as claimed in claim 14, wherein eachof said tangential tabs delimits at least in part the respective guidechannel.
 18. Grass-cutting head as claimed in claim 14, wherein saidtabs can engage reversibly by means of a hook-shaped end in a seat of arespective projection and can be locked, by means of a screw member, apin or the like, to said projection in proximity to the outlet hole ofthe line.
 19. Grass-cutting head as claimed in claim 1, furthercomprising a second outlet and respective guides for the cutting line.20. Grass-cutting head as claimed in claim 1, wherein said bodycomprises: a cup portion, defining a housing for the spool; an annularportion coupled to said cup portion, defining, together with said cupportion, said guide channel; and a removable closing member. 21.Grass-cutting head as claimed in claim 20, wherein said cup portion andsaid annular portion have respective approximately spiral-shapedprojections, inside which said guide channel is defined. 22.Grass-cutting head as claimed in claim 20, wherein said closing memberhas a substantially circular wall with elastic tabs which engagereleasably with the annular portion of the body of the head. 23.Grass-cutting head as claimed in one or more of claim 20, wherein theclosing member has a central hole, through which a button projects tocontrol unwinding of the line from the spool.
 24. Grass-cutting head asclaimed in claim 1, wherein said guide channel has an extension along anangle equal to at least 30° and preferably equal to or greater than 45°and even more preferably equal to or greater than 60° about the axis ofrotation of said grass-cutting head.
 25. Grass-cutting head as claimedin claim 24, wherein said guide channel has an extension along an angleequal to or greater than 80° and preferably between 80° and 120° aboutthe axis of rotation of the head. 26-28. (canceled)
 29. A grass-cuttinghead with an axis of rotation, the grass-cutting head comprising: a bodyforming a housing for at least one spool of cutting line, provided withat least one outlet hole of an end of said cutting line wound on saidspool, said body having an external toothed profile, a respective outlethole of the cutting line being arranged at the level of each tooth ofsaid profile.
 30. Grass-cutting head as claimed in claim 29, whereineach tooth of said toothed profile has a first side inclined by an angleof no more than 45° and preferably between 0° and 30° with respect to aradial direction, on which the respective outlet hole of the line isproduced.
 31. Grass-cutting head as claimed in claim 30, wherein eachtooth has a second curvilinear side with a preferably spiral shape. 32.Grass-cutting head as claimed in claim 30, wherein a guide channel forthe cutting line extends inside each of said teeth.
 33. Grass-cuttinghead as claimed in claim 31, wherein the second side of each tooth has agreater extension with respect to the first side, and wherein said holeis provided on the first side of the respective tooth.
 34. Grass-cuttinghead as claimed in claim 2, wherein said channel and said outlet holeare produced in portions of the body of the head projecting with respectto a substantially cylindrical surface of said body, the hole beinglocated on a surface which intersects said substantially cylindricalsurface.
 35. Grass-cutting head as claimed in claim 2, wherein theoutlet hole defines a direction of projection of the line from the bodyof the head which is not radial and preferably inclined by an anglebetween 30° and 90° and more preferably between 60° and 90° with respectto a radial direction and even more preferably between 60° and 90°. 36.Grass-cutting head as claimed in claim 14, wherein said projection ismade integral with said body, with the same material of which said bodyis formed or with a different material.